In general, a magneto AC generator for a vehicle includes a generator coil to operate loads such as lamps and a generator coil to supply a charging current through a rectifier mainly to a battery on the vehicle. Conventionally, such a magneto AC generator comprises a voltage regulator including controlled rectifiers arranged to be connected in parallel to the loading and battery charging generator coils, respectively, which serve to short-circuit the corresponding generator coil when the respective generator coils have the output voltages generated over a predetermined value whereby the output voltage are regulated. Such a voltage regulator, however, has the disadvantage in that the construction is very complicated because of two controlled rectifiers being required.